Releasable balloon catheter

ABSTRACT

This invention provides a releasable balloon catheter having a portion cuttable by torsion or a portion cuttable by heating at or near a joint part between the catheter body and the balloon. When the balloon catheter is inserted into a vessel and carried to the desired site by the blood stream and the balloon is inflated by introducing a fluid into the balloon and is fixed at the desired site face-to-face with the wall of the vessel, torsion or heating causes the balloon to be released from the catheter body. The balloon catheter is used to embolize vascular lesions.

This is a division of application Ser. No. 121,036, filed Feb. 13, 1980,now U.S. Pat. No. 4,346,712.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a releasable balloon catheter, and morespecifically, to a releasable balloon catheter for use in occluding orembolizing a vascular lesion.

2. Description of the Prior Art

Catheters have been used as essential medical instruments for diagnosisand treatment. In recent years, it has been made possible to insert aso-called balloon catheter having at its tip an inflatable andshrinkable balloon into the inside of a minute vessel along a bloodstream, which cannot be reached by means of conventional catheters notprovided with a balloon. This has further increased the range ofapplication of catheters.

If an inflated balloon can be released from the tip of a catheter at thedesired site, the treatment of various vascular lesions, which has beenimpossible by conventional techniques, will be able to be achieved. Anexample is the application of balloon catheters to the treatment ofaneurysm, arteriovenous malformation and arteriovenous fistula which aretypical vascular disorders. For example, by keeping an inflated balloonwithin an aneurysm, a serious sequela in the event of rupture of theaneurysm can be prevented. Or by occluding a vessel leading to amalformed arteriovein with a released ballon, a sequela of arteriovenousmalformation incident to bleeding can be prevented. Furthermore, if anarteriovenous fistula can be occluded, the blood flow in an artery canbe restored to one close to a normal condition.

As is clear from a few examples given herein, if a catheter having areleasable balloon is developed, it will be a great boon to patientssuffering from cerebrovascular disorders and cardiovascular disorderswhich occupy the first and third places, respectively, of mortality inJapan. The great significance of the development of such a catheter isclear in view of the fact that this new method of treatment does notrequire any surgical operation, but can be achieved simply by injection.

The site at which the balloon is desired to be released is mainly avascular lesion which is located deep inside the body. Accordingly, itis required that the balloon should not be released from the mainportion of the catheter until it reaches this site, and that the balloonshould be released even at such a site which is deep inside the body.

Prior to the present invention, two types of catheter with a releasableballoon have been devised for vascular occlusion. In one type, firstreported by Debrun (Neuroradiology 1975, 9:267˜271 and J. Neurosurgery1978, 49:635˜649), the balloon is firmly tied to a Teflon catheter withelastic threads and is released with the help of a second coaxialpolyethylene catheter. The disadvantage of this type is that thecatheter is difficult to introduce beyond many arterial curves such asthe carotid siphon, because of its lack of flexibility. Its use alsorequires a relatively large coaxial catheter. The other has beenreported by Serbinenko (U. Neurosurgery 1974, 41:125˜145), who attachesa balloon to a polyethylene catheter which grips the catheter due to itselasticity. The balloon is released simply by pulling on the catheter.This type of catheter can be used with lesions on many branches of thearterial tree. It has the danger that it can be released accidentally.It can also damage the vascular lesion if it is pulled on.

An attempt was made to remedy these defects. Japanese Laid-Open PatentPublication No. 132580/1977 discloses a balloon catheter in which theballoon is fixed to the main portion of the catheter by securing aC-type spring to a joint part between them. In such a balloon catheter,the C-type spring is released when the pressure in the balloon exceeds aspecified limit by the pressure of a fluid introduced into the balloon.Thus, the balloon is released from the catheter. However, the ballooncatheter of this type has the disadvantage that there are some caseswhere the balloon is released in a place other than the desired site andcannot be released when desired, because it is difficult to adjust thepressure applied by the C-type spring.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a releasableballoon catheter which can be easily inserted into vessels and which canbe released at the desired site with certainty.

Another object of this invention is to provide a releasable ballooncatheter which can be inserted into minute vessels and does not injurethe walls of the vessels.

Still another object of this invention is to provide a releasableballoon catheter which can be easily produced.

These objects can be achieved by a releasable balloon catheter including(i) a tubular catheter body, (ii) an inflatable balloon provided at oneend of the catheter body so that a fluid is introduced into the balloonfrom the catheter, and (iii) (a) a tube cuttable by torsion or (b) atube cuttable by heating, the tube (a) or (b) being provided at or neara joint part between the balloon and the catheter body, the ballooncatheter being constructed such that when said balloon cathether isinserted into a vessel and carried to the desired site by the bloodstream and the balloon is inflated by the introduction of a fluid intothe balloon through the catheter body and is fixed face-to-face with thewall of the vessel at the desired site, a torsional force is applied tothe tube (a) cuttable by a torsion or heat is applied to the tube (b)cuttable by heating, thereby to effect cutting at the cuttable tube (a)or (b) and thus to release the balloon from the catheter body.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects of this invention wil become apparent from the followingdescription.

FIG. 1 is a longitudinal sectional view showing one example of theballoon catheter of this invention which contains a tubular member 2 asa portion cuttable by torsion;

FIG. 2 is a longitudinal sectional view showing another example of theballoon catheter of this invention which further has a cover 8 forpreventing the flexural breaking of the tubular member 2 at the time ofinsertion into a vessel;

FIG. 3 is a longitudinal sectional view of still another example of theballoon catheter of this invention which has a rigid core material 6inserted into the cavity of the tubular member 2 cuttable by torsion toprevent the flexural breaking of the member 2 at the time of insertioninto a vessel;

FIG. 4 is a longitudinal sectional view of a further example of theballoon catheter of this invention which has X-ray impervious metallicpieces 7 secured thereto so that the cutting of the tubular member 2cuttable by torsion within a vessel can be ascertained;

FIG. 5 is a longitudinal sectional view showing another embodiment ofthe balloon catheter of this invention which contains a notched portion2 as the portion cuttable by torsion at the end of a catheter body 1;

FIG. 6 is a longitudinal sectional view showing yet another example ofthe balloon catheter of this invention, which has provided therein atubular member 2 as the portion cuttable by heating, which is adapted tobe heated by electrodes 12 and 13 composed of conductor wires;

FIG. 7 is a cross-sectional view taken along the line 7--7 of FIG. 6;

FIG. 8 is a longitudinal sectional view showing another example of theballoon catheter of this invention, which has provided therein a tubularmember 2 as the portion cuttable by heating, which is adapted to beheated by electrodes 19 and 20 composed of conductive metallic foil;

FIG. 9 is a cross-sectional view taken along the line 9--9 of FIG. 8;

FIG. 10 is a longitudinal sectional view showing another example of theballoon catheter of this invention, which has provided therein a tubularmember 2 as the portion cuttable by heating, which member is adapted tobe heated by a monopolar electrode 21;

FIG. 11 is a cross-sectional view taken along the line 11--11 of FIG.10;

FIG. 12 is a longitudinal sectional view showing another example of theballoon catheter of this invention, which includes a tubular member 2cuttable by heating, conductor wire electrodes 12 and 13 and a rigidcore material 6 for preventing the flexural breaking of the member 2 atthe time of insertion into a vessel;

FIG. 13 is a longitudinal sectional view showing another example of theballoon catheter of this invention, which includes a tubular member 2cuttable by heating, conductor wire electrodes 12 and 13, and a cover 8for preventing the flexural breaking of the member 2 at the time ofinsertion into a vessel;

FIG. 14 is a longitudinal sectional view of another example of theballoon catheter of this invention, which includes a tubular member 2cuttable by heating, conductor wire electrodes 12 and 13, and X-rayimpervious metallic pieces 7 for ascertaining the cutting of the member2 within the vessel; and

FIG. 15 is a longitudinal sectional view showing one example of aninjector for inserting the balloon catheter of this invention into avessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the balloon catheter of this invention includes (i)a tubular catheter body 1, (ii) an inflatable balloon 3 provided at oneend of the catheter body so that a fluid is introduced into the balloonfrom the catheter, and (iii) a portion 2 cuttable by torsion provided ata joint part between the balloon and catheter body. The other end of thecatheter is not shown in the drawings. Usually, the catheter 1 extends apredetermined length (the length being selected as desired dependingupon the desired use) to form the other end into which an injectingsyringe is usually inserted for introduction of a fluid into thecatheter by an injector. The portion 2 cuttable by torsion is made of atube having a weaker torsion strength than the catheter body 1. When theother end of the catheter body which is not inserted into a vessel istwisted, cutting occurs at this tube 2. The tube 2, the catheter body 1and the balloon 3 are connected to each other by an adhesive (e.g.cyanoacrylate or epoxy type adhesives). Resin layers 4 and 5 are formedso that the catheter body, tube and balloon are connected to each othercontinuously to form a smooth surface. If the joint part between thetubular member 2 and the catheter body 1 is smoothed by means of anadhesive 4, the balloon catheter will not injure vessels at the time ofcatheterization.

FIG. 2 shows another embodiment of the balloon catheter of thisinvention. This embodiment is preferred when the tubular member 2 has alow flexibility and is likely to be broken upon bending at the time ofcatheterization. A cover 8 is provided at the terminal portion of thecatheter body 1 so as to cover the member 2. The cover 8 is cemented bymeans of an adhesive 9. Preferably, the cover 8 is made of a tubularmaterial having resistance to breakage upon bending (for example,silicone rubber). A sheet 11 which is made of polyethylene tube, etc.,is provided to prevent bending breakage of the balloon 3 and further tofacilitate catherization. The sheet 11 is fixed to the balloon 3 and themember 2 by adhesives 5 and 10. In FIG. 2, as a result of providing thecover 8 and the sheet 11, there is some gap between the tip of the cover8 and the end of the balloon 3. Hence, the member 2 is prevented frombending and breaking. Furthermore, since the top surface of the cover 8and the top surface of the balloon 3 are smooth, the catheter can beeasily inserted into a vessel and does not injure the vascular walls.

Still another embodiment in which the member 2 has low flexibility andis likely to be broken upon bending is shown in FIG. 3. In thisembodiment, a rigid core material 6 (e.g., a nylon fishing gut or aresin-dipped polyester thread is inserted into the cavity of the member2 to prevent the flexural breaking of the member 2. When this ballooncatheter is inserted into a vessel and the balloon is to be releasedwithin the vessel, the core material 6 is pulled out immediately beforethe releasing of the balloon.

When the member 2 is likely to be broken upon bending at the time ofinserting an intravenous catheter, it is also possible to coat theperiphery of the member 2 with a hydrophilic polymer, especially awater-soluble polymer such as polyvinyl alcohol, starch or dextran. Thewater-soluble polymer to be coated at this time should be non-toxic evenwhen it dissolves in the blood.

Referring to FIG. 4, an X-ray impervious metallic piece 7 is fixed toboth sides of a tubular member 2, i.e. to the terminal portions of theballoon and the catheter body. The piece is made of a material such asstainless steel, titanium or cobalt-chromium alloy. This constructionenables the distance between the two metallic pieces to be known byradiography. It is possible therefore to ascertain that the tubularmember is twisted off within a vessel to release the balloon.

Still another embodiment of this invention is shown in FIG. 5. In thisembodiment, a notched portion 2 is provided at the periphery of theterminal portion of the catheter body 1 as a portion which can be cut bytorsion. Preferably, the portion is provided within 10 mm (morepreferably 1 mm) from the terminal portion of the catheter body.

The balloon catheter shown in FIG. 5 has the disadvantage that themember 2 is liable to be broken at the notched portion when insertedinto the blood vessel. Further, the member 2 is more difficult toproduce than that shown in FIG. 1. Therefore, this embodiment is notpreferred.

The individual portions of the above embodiments, i.e., the ballooncatheters having a portion cuttable by torsion, are described in detailbelow.

One characteristic feature of this invention is that a portion which iscuttable by torsion is provided in a balloon catheter. When this portionis to be composed of a tubular material, it must have a lower torsionalstrength than the catheter body. The torsion strength of the member 2 isdetermined according to the site of a vessel used. The member 2 is inthe form of a tube or hollow fiber, and its thickness, outside diameterand length cannot be determined according to a single parameter becausethey depend upon the size and shape of a vessel to be occluded. Usually,the member 2 has a wall thickness of 10 to 400 microns, preferably 10 to200 microns, an outside diameter of 100 to 1000 microns, preferably 200to 700 microns, and a length (the length from the end of the balloon 3to the end of the catheter body 11 of 2 to 20 mm, preferably 2 mm to 15mm.

The material for the member 2 may be any material which meets the abovephysical conditions. Examples include polyethylene, polypropylene,polyvinyl alcohol, vinyl alcohol copolymers (such as an ethylene-vinylalcohol copolymer with an ethylene content of 10 to 60 mole%), nylon,polyethylene terephthalate, regenerated cellulose, and cellulosederivatives. Polyvinyl alcohol, vinyl alcohol copolymers and regeneratedcellulose are preferred. The above polyvinyl alcohol includes acetalizedpolyvinyl alcohol obtained by acetalization with formaldehyde,glutaraldehyde, etc. to a degree of acetalization of 1 to 50 mole%.

The outside diameter and the wall thickness of the catheter body 1 aredetermined according to a vessel into which it is inserted, and arewithin the same ranges as those described above for the member 2.Usually, the catheter body has a slightly larger outside diameter thanthe member 2. It is necessary that the catheter body 1 should have ahigher torsion strength than the member 2. It should have a tensilestrength such that it does not break upon catheterization. Preferably,the catheter body 1 is a thin tube, for example, a hollow fiber, havinga Young's modulus in the wet state (in water at 25° C.) of 1 to 100 kg,preferably 2 to 20 kg, so as to permit easy insertion into minute, bentvessels. The Young's modulus is measured by using an ordinary tensiletester at a tensile speed of 10 cm/min. in water at 25° C. using asample having a length of 5 cm. The material for the catheter body 1 maybe the same as those described above for the member 2. Preferably, it ismade of polyethylene or teflon which is used in ordinary catheterbodies.

The balloon 3 used in this invention may be made of a material which hasrequired elasticity and can endure sterilization. Rubbers (natural,synthetic and silicone rubbers) are preferred. The shape and size of theballoon 3 are determined depending upon the type of a vessel. Usually,it is in the form of a cylindrical cap shown in the drawings. To permiteasy insertion into bent minute vessels, the balloon in the non-inflatedstate should have as small a thickness as possible, for example lessthan 500 microns, preferably less than 200 microns.

Now, a balloon catheter having a portion which is cuttable by heating isdescribed in detail. FIG. 6 shows one example of this type. The ballooncatheter has a portion 2 cuttable by heating between a catheter body 1and a balloon 3. This portion 2 is a tubular member composed of amaterial which is melted or dissolved in blood when heated. Bipolarelectrodes 12 and 13 composed of conductor wires are secured to theportion 2 so as to heat the tube whenever necessary.

The tubular member 2 which is melted by heating is a solid at the bodytemperature. A suitable material for it is one which does not easilybreak by an external force, is easily melted or dissolved within avessel at a temperature above the body temperature but below thetemperature at which water is vaporized (100° C.), and which is nottoxic to the living body even when melted or dissolved in the blood.Preferably, the material should be easily processable, and be flexible.An example of such a material for the member 2 is a hydrophilic polymer.Above all, polyvinyl alcohol and vinyl alcohol copolymers (e.g., anethylene/vinyl alcohol copolymer having an ethylene content of 10 to 60mole%) are suitable. The shape of the member 2 is a tube or hollow fiberas described hereinabove. Its outside diameter, thickness and lengthcannot be determined according to a single parameter because they dependupon the size and shape of a vessel to be occluded. Usually, it has anoutside diameter of 100 to 1000 microns, preferably 200 to 700 microns,a wall thickness of 10to 400 microns, preferably 10 to 200 microns, anda length (the length from the end of the balloon 3 to the end of thecatheter body 1) of 2 to 50 mm, preferably 5 to 30 mm.

The bipolar electrodes 12 and 13 may be provided not only exteriorly ofthe member 2 as shown in FIG. 6, but also interiorly of the member 2 ormay be embedded in the member 2. These electrodes 12 and 13 areconnected to a high frequency current generator 18 through lead wires 14and 15. The member 2 is melted as a result of the high frequency currentpassing across the electrodes 12 and 13. Preferably, the distancebetween the electrodes 12 and 13 is as short as possible because themember 2 can be melted or dissolved more exactly within a shorter periodof time. The lead wires 14 and 15 are electrically conductive, and aremade of a material which is free from leakage, allows only a minimum ofheat generation, is flexible, and which can be very intricatelyprocessed. For example, enamelled copper wires are preferred. The leadwires 14 and 15 lead to the high frequency current generator 18 alongthe outside of a tube 17 provided at the other end of the ballooncatheter through a bonded part 16 between the tube 17 and the catheterbody 1.

When a very flexible catheter body is used, a heating mechanismutilizing a high frequency current as shown in FIG. 6 is preferred. Whenthe catheter body is slightly hard and has such a flexibility of fiberas to permit transmission of laser, the heating mechanism may be the onebased on laser.

The member 2, balloon 3 and catheter body 1 are bonded to each other bymeans of an adhesive (e.g., cyanoacrylate or epoxy type adhesives). Inthis case, as in the balloon catheter shown in FIG. 1, adhesive layers 4and 5 are formed so that the bonded portions between the member 2 andthe balloon 3 and the catheter body 1 form a smooth surface (see FIG.6). The balloon used in this invention is the same as that describedhereinabove. The catheter body used in this embodiment may be the sameas that described hereinabove. It may also be made of a siliconepolymer, polyurethane, thermoplastic polyesters (e.g., polybutyleneterephthalate), a silicone-polyurethane copolymer, soft vinyl chlorideresin, and an ethylene/vinyl acetate copolymer. Of these, silicones arepreferred. When the tubular member is to be cut off by torsion, thetorsion strength of the catheter body needs to be higher than that ofthe tubular member. Thus, the catheter body is required to have acertain hardness. Accordingly, the catheter body in this case shoulddesirably have a Young's modulus within the above-specified range.However, in the case of the balloon catheter shown in FIG. 6, suchproperties are not required, and a flexible material may be used.

In FIG. 8, electrodes 19 and 20 composed of conductive metal foil areplaced on the top and bottom of the member 2 as heating mechanism, andeach end of the metal foils is secured to the member 2 by an adhesive 4.

In FIG. 10, a monopolar electrode 21 composed of a bare conductive wireis wrapped around the member 2 as a heating mechanism. A conductor wire22 is connected to a high frequency current generator 18, and anotherconductor wire 29 leads from an opposite electrode on the body surface30 of a patient to the high frequency current generator 18. Generally,the electrode which is made of a metal plate (50×30 cm) is set on theback, the belly or the thigh of the patient.

When the member 2 is likely to be broken upon bending incatheterization, it is possible to insert a core material into the innercavity of the member 2 (FIG. 12), or to provide a cover so as to coverthe tubular member (FIG. 13). The space 31 shown in FIG. 13 may befilled with a viscous aqueous solution containing water soluble polymer,for the purpose of preventing the thrombus which is likely to be formedat the time of contact of blood with the heated portions. The embodimentshown in FIG. 14 is used when it is necessary to ascertain that thetubular member is cut off by heating and the balloon is released.

Among the various embodiments described above, the embodiments shown inFIGS. 6 and 13 are frequently used. When a balloon catheter having aportion cuttable by torsion is compared with that having a portioncuttable by heating, it is noted that the former (torsion-type) requiresa certain degree of hardness at its body portion, and therefore, as faras cerebral vessels are concerned, it is useful for occluding thesupracellosal portion of the anterior cerebral artery and M3 portion ofthe middle cerebral artery, but is difficult to use for occlusion ofmore distal vessels. A torsional force can be transmitted well when thecatheter is short. But when the catheter is long, for example when avascular lesion of the basilar artery is to be occluded via the femoralartery, the torsional force is difficult to transmit. Thus, to transmitthe torsional force well, a considerable length of the catheter fromthat end at which the torsional force is to be applied should be made ofa hard material. Accordingly, the balloon catheter having a portioncuttable by heating is better.

The releasable balloon catheter of this invention is used in thefollowing manner. The balloon catheter is introduced into a vessel, andby carrying the inflated balloon along a blood stream, the ballooncatheter is conveyed to the desired vascular site. Then, through thecatheter body, a curable liquid, etc. is introduced into the balloon toinflate the balloon further so that the balloon adheres closely, and isfixed, to the vascular wall at the desired site. Then, by applying atorsional force or heating, the cuttable portion of the tubular memberis cut off to release the balloon. When it is necessary to ascertain thereleasing of the balloon at this time, balloon catheters of the typesshown in FIGS. 4 and 14 are used.

Since the releasable balloon catheter of this invention is of verysimple structure as described above, it is easy to produce at a lowcost. It is also safe because the balloon is never released from thecatheter body unless a torsional force is applied to the catheter or theseverable tube is heated to a temperature above the body temperature.Furthermore, because the severable tube is cut off accurately, theballoon does not deviate from the desired site, and is released withoutinjuring the vascular wall. Accordingly, the balloon catheter of thisinvention is very useful.

The following Examples illustrate the present invention morespecifically. The invention, however, is not limited in any way by theseexamples.

EXAMPLE 1

As a member 2, a slender tube (outside diameter 250 microns, thickness20 microns) made of cellulose was inserted into a vulcanized naturalrubber balloon (outside diameter 400 microns, thickness 100 microns inthe shrunken state) as shown in FIG. 1, and they were fixed to eachother by a cyanoacrylate type adhesive 5. The cellulose tube was cut ata position 1 cm from the end of the balloon. A 1 mm portion of the otherend of the cellulose tube was inserted into a chromic acid-treatedcatheter body 1 (made of polyethylene and having an outside diameter of600 microns, a wall thickness of 180 microns and a length of 60 cm), andthis portion was bonded by using a cyanoacrylate-type adhesive. Thecellulose tube used had a tensile strength of 56 g and a torsionstrength of 29 g. The polyethylene catheter had a tensile strength of645 g, a Young's modulus of 3.8 kg, and a torsion strength of 108 g.These were measured in the wet state at 21° C. The torsion strength wasmeasured by a tensile tester (Instron TMM) at a speed of 100 times/min.while adjusting the length of a sample to 5 cm.

After confirming that the bonding between the balloon and the cellulosetube and the bonding between the cellulose tube and the polyethylenecatheter were sufficient, and the resulting balloon catheter hadsufficient strength to repeated inflation and shrinkage by injectingwater into the catheter from the other end of the polyethylene catheterusing an injector, the balloon catheter was inserted into a longsilicone tube having an inside diameter of 5 cm. Then, the balloon wasinflated by water to bring the balloon wall into intimate contact withthe inside wall of the silicone tube. When the end of the catheter wasrotated by fingers, the cellulose tube was twisted off after six cyclesof rotation, namely after giving six torsions to the catheter, and theballoon was released. Within about several minutes, the water inside theballoon flowed out, and the balloon shrank.

The above balloon catheter was inflated with a curable vinyl monomerliquid instead of water, and after the filled liquid cured, 7 cycles ofrotation were given to the catheter. The balloon was thus released fromthe tip of the catheter, and remained inflated even after one day.

EXAMPLE 2

As a member 2, a slender tube (outside diameter 350 microns, wallthickness 35 microns) made of an ethylene/vinyl alcohol copolymer(ethylene content 33 mole%, to be referred to as EVA) having a tensilestrength of 42 g and a torsion strength of 10 g was cemented to avulcanized natural rubber balloon 3 (outside diameter 800 microns, wallthickness 100 microns in the shrunken state) through a sheet 11 composedof a polyvinyl alcohol tube by cyanoacrylate-type adhesives 5 and 10, asshown in FIG. 2. The EVA tube 2 was cut at a position 5 mm from the endof the balloon. Separately, a silicone tube cover 8 was fixed to theperiphery of the end portion of the same mixed chromic acid-treatedcatheter body 1 (polyethylene catheter having an outside diameter of 600microns, a wall thickness of 180 microns and a length of 60 cm) as usedin Example 1 by means of a cyanoacrylate-type adhesive 9. A 1 mm portionof the end of the EVA tube 2 produced as above was inserted into thepolyethylene catheter, and the EVA tube 2 and the polyethylene catheter1 were conded by means of a cyanoacrylate-type adhesive. After bonding,an epoxy-type adhesive was coated on a bonded peripheral portion 9 tomake it smooth, and then allowed to solidify. The EVA tube fully adheredboth to the balloon and the polyethylene catheter, and when the balloonwas repeatedly inflated and shrunken by flowing water therethrough, theballoon catheter had sufficient strength.

When the releasable balloon catheter thus obtained was inserted into asilicone tube and subjected to a torison test, the balloon was cut offfrom the catheter body after ten cycles of torsion. Because of theself-fusing property of EVA, the balloon remained inflated even after alapse of 2 hours.

EXAMPLE 3

An adult dog was anesthetized with Nembutal, and then its left externalcarotid artery was punctured with an 18-gauge, 13 cm intravenouscatheter. The inside portion was pulled out, and the outside Tefloncatheter was inserted into a vessel. Through the Teflon catheter, thesame releasable balloon catheter as produced in Example 2 was insertedinto the vessel. The balloon catheter was conducted to the branch of theexternal carotid artery while inflating the balloon under X-rayfluoroscopy. After conducting the balloon to a site of occulsion, it wasshrunken and the angiografin (contrast medium) in it was fully removed.A mixed liquid obtained by mixing a silicone primer and tetraethylortho-silicate in a ratio of 1:1 and adding a moderate amount of tinoctylate was injected into the balloon. After the silicone was cured,the catheter was rotated. Thus, the EVA portion was twisted off, and theballoon was released from the catheter. The balloon stayed at the siteof occlusion, and fully acted as an embolizing means.

EXAMPLE 4

The left neck of a patient with intracranial arteriovenous malformationof the corpus callosum was locally anesthetized with dibucaine, and thecommon carotid artery was punctured with an 18-gauge, 13 cm intravenouscatheter. The outer Teflon sheath was inserted in the direction of theinternal carotid artery under X-ray fluoroscopy. The same releasableballoon catheter as produced in Example 2 was inserted through theTeflon sheath. The balloon was inflated with a contrast medium, and ledto the branch of the anterior cerebral artery along a blood stream. Theanterior cerebral artery was a feeding artery of the intracranialarterivenous malformation of this patient. By embolizing it, theintracranial arteriovenous malfunction could be treated. The balloonthus guided was temporarily shrunken, and the angiografin (contrastmedium) in it was fully removed. Then, a mixed liquid obtained by mixinga silicone primer and tetraethyl ortho-silicate in a ratio of 1:1 andadding tin octylate was injected into the balloon. After the balloonoccluded the branch of the anterior cerebral artery and the silicone wascured, the catheter was rotated to release the balloon from thecatheter. No complication owing to this operation was noted.

EXAMPLE 5

As shown in FIG. 6, a natural rubber balloon 3 (outside diameter 800microns, wall thickness 100 microns in the shrunken state) was securedto a polyvinyl alcohol tube 2 (outside diameter 500 microns, wallthickness of 100 microns), and they were bonded to each other by acyanoacrylate-type adhesive. The bonded portion was coated with an epoxyresin to form a smooth surface. Two enamelled wires 14 and 15 (0.05 mmin diameter) were inserted through a silicone tube 1 (outside diameter600 microns). From one end of the silicone tube, the enamelled wireswere pulled outwardly, and the polyvinyl alcohol tube 2 was insertedinto the silicone tube 1. They were bonded by a cyanoacrylate-typeadhesive. The bonded portion was coated with an epoxy resin 4 to form asmooth surface. One of the enamelled wires pulled outwardly was broughtto the end portion of the polyvinyl alcohol tube and loosely wrappedaround it in a loop form after removing a part of the enamel, therebyforming an electrode 12. An electrode 13 produced by removing part ofthe enamel of the other enamelled wire was similarly wrapped around thecentral portion of the polyvinyl alcohol tube. The distance between theelectrodes 12 and 13 was made as short as possible and adjusted to about1.3 mm. On the other hand, the two enamelled wires extending from theother end of the silicone tube 1 were pulled out of the silicone tube,and a chrome-treated polyethylene tube 17 (outside diameter 600 microns,wall thickness 180 microns) was fitted into one end of the silicone tubeand they were bonded by a cyanoacrylate-type adhesive. The bondedportion was coated with an epoxy resin 16 to form a smooth surface.After confirming that the sealing of the lead wire pulling portion wascomplete, short-circuiting between the electrodes 12 and 13 and betweenthe lead wires 14 and 15 and the breaking of the lead wires wereexamined by testers. The balloon catheter was dipped in physiologicalsaline, and then the enamel coating of the lead wires extendingoutwardly of the polyethylene tubing was removed, and the lead wireswere connected to a high frequency current generating device 18 (aproduct of Aesclup Company). A curable liquid comprising 2-hydroxyethylmethacrylate and a polymerization initiator was injected into theballoon, and cured. Then, the output (Dosis) of the high frequencycurrent generator was set at 3, and power was supplied. In about 1second, the bonded portion 2 composed of the polyvinyl alcohol tube wasdissolved, and the balloon 3 was separated from the catheter body 1 madeof silicone tube.

EXAMPLE 6

An adult dog was anesthetized, and an arteriovenous fistula wasartifically made by the anastomosis of the external jugular vein and thecommon carotid artery. A sheath introducer having an Fr (French unit) of5.5 was inserted into that portion of the carotid artery which was moreon the heart side than the fistula. A balloon catheter produced in thesame way as in Example 5 was inserted through the introducer. On theother hand, the lead wires and electrodes in the balloon catheter werewell examined by testers to confirm that there was no short-circuitingbetween them. Since a silicone catheter was very flexible and could notbe injected in opposition to the back flow of the blood from the sheath,it was injected as included in an injector 23 as shown in FIG. 15.Specifically, the balloon catheter was included in the injector 23, andinjected into a vessel together with physiological saline 24 in theinjector 23. In FIG. 15, the reference numeral 25 represents the tip ofa rubber plunger, and 27, the outlet of the injector. The referencenumeral 26 represents a metallic tube extending through the plunger tip25. The silicone tube was passed through the metallic tube 26, and thespace between them was sealed up with a resin. The reference numeral 28represents a 1 cc syringe for introduction of a contrast medium, etc.

Then, the balloon was inflated with a contrast medium (metrizamide), andconducted to fistula portion. After the contrast medium was removed asmuch as possible, a photographable curable liquid comprising2-hydroxyethyl methacrylate and a polymerization initiator was injectedinto the balloon to inflate it and thereby to embolize the fistulaportion. After the liquid was cured, the lead wires were connected to ahigh frequency current generator (a product of Aesclup Company). Whenpower was supplied for 1 second at an output (Dosis) of 3, the balloonwas released from the catheter body. It was ascertained that only thefistula portion was occluded, and the four streams of the carotid arterywere preserved.

The dog used in the experiment awoke well from anesthesia, and noadverse effect owing to this operation was seen to be exerted on theexperimental animal.

EXAMPLE 7

An adult dog was anesthetized, and an arterial fistula was artificiallymade at the common carotid artery using a graft segment of the externaljugular vein. In the same way as in Example 6, the same balloon as usedin Example 5 was conducted to the arterial fistula. The same curableliquid as in Example 2 was injected into the balloon. After the liquidwas cured, power was supplied at an output (Dosis) of 3 for 1 second torelease the balloon. It was ascertained that the balloon occluded onlythe arterial fistula, and there was no constriction in the carotidartery. No adverse effect was seen to be exerted on the experimentalanimal.

EXAMPLE 8

An arteriovenous fistula was made artificially by anastomosing thecommon carotid artery and the external jugular vein in an adult dog. Apolyethylene catheter having an Fr of 6.0 was inserted through the rightfemoral artery, and guided to the right carotid artery by theSeldinger's method. The same balloon catheter as produced in Example 5was included in an injector in the same way as in Example 6 and 7, andinserted into the carotid artery by the injector shown in FIG. 15through the above catheter. The balloon was similarly guided to thefistula portion. Then, the same curable liquid as in Example 6 wasinjected to occlude the fistula portion by the balloon. Power wassupplied for 1 second at an output (Dosis) of 3 using a high frequencycurrent generator to release the balloon. No adverse effect was exertedon the dog.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A releasable balloon catheter, comprising:atubular catheter body; an inflatable balloon provided at one end of saidcatheter body so that a curable liquid may be introduced into theballoon from the catheter; a severable tube formed at a joint partbetween said balloon and said catheter body; said balloon catheter beingconstructed such that when said balloon catheter is inserted into avessel and carried to the desired site by the blood stream and theballoon is inflated by the introduction of said curable liquid into theballoon through the catheter body and is fixed face-to-face with thewall of the vessel at the desired site, said severable tube is severedwhen a torsional force is applied thereby cutting said severable tubeand releasing said balloon from said catheter.
 2. The releasable ballooncatheter of claim 1, wherein said severable tube further comprises atube having an outside diameter of 100 to 1000 microns, a wall thicknessof 10 to 400 microns and a length of 2 to 50 mm and a lower torsionstrength than said catheter body.
 3. The releasable balloon catheter ofclaim 1, wherein said catheter body further comprises a polyethylenetube and said severable tube connecting said balloon to said cather bodyfurther comprises a polyvinyl alcohol tube.
 4. The releasable ballooncatheter of claim 1, wherein said catheter body further comprises apolyethylene ethylene tube and said severable tube connecting saidballoon to said catheter body further comprises an ethylene/vinylalcohol copolymer tube.
 5. The releasable balloon catheter of claim 1,wherein said catheter body further comprises a polyethylene tube andsaid severable tube connecting said baloon to said catheter body furthercomprises a regenerated cellulose tube.
 6. The releasable ballooncatheter of claim 1, further comprising a cylindrical cover coveringsaid severable tube at the joint part between said balloon and saidcatheter body so that said tube is prevented from flexural breaking uponcatheterization.
 7. The releasable balloon catheter of claim 1, furthercomprising a rigid core material in the inner cavity of said ballooncatheter so that the severable tube at the joint part between saidballoon and said catheter body is prevented from flexural breaking uponcatheterization.
 8. The releasable balloon catheter of claim 1, furthercomprising an X-ray impervious metal piece secured to the end portion ofsaid catheter body and to said balloon so as to ascertain the releasingof the balloon from the catheter body by X-ray fluoroscopy.
 9. Thereleasable balloon catheter of claim 1, further comprising a notchprovided on the surface of said severable tube, whereby said severabletube is cut at said notch.